WO2002035702A1

WO2002035702A1 - Surface acoustic wave filter

Info

Publication number: WO2002035702A1
Application number: PCT/JP2001/009303
Authority: WO
Inventors: Ryoichi Takayama; Hidekazu Nakanishi; Tetsuo Kawasaki; Toru Sakuragawa; Yasuhiko Yokota
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2000-10-23
Filing date: 2001-10-23
Publication date: 2002-05-02
Also published as: EP1330026A4; EP1330026A1; JP4059080B2; JPWO2002035702A1; CN1394388A; US6909341B2; KR100791708B1; EP2458735A3; KR20020062661A; CN1551496A; EP2458735A2; US20030174028A1; CN1190007C

Abstract

In a surface acoustic wave (SAW) filter having a substrate and electrodes formed on the substrate, an electrode has a base layer, a first metal layer made of Al or an Al-based metal and oriented in a constant direction to the substrate, a second metal layer which prevents Al atoms of the first metal layer from migrating vertically to the substrate, and a third metal layer for adjusting the film thickness. Thus, a SAW filter having an arbitrary film thickness enables the simultaneous attainment of a film quality of difficulty in grain boundary diffusion and micronization of the grain diameter of a film effective in stress resistance. Therefore, the SAW filter blocks the migration of Al atoms of the electrode due to a stress loaded on the electrode with the propagation of the SAW, so that the filter becomes excellent in power resistance.

Description

Description Surface acoustic wave filter Technical field

The present invention relates to an elastic surface acoustic wave filter having electrodes formed on a substrate, such as a comb-shaped electrode, and a method for manufacturing the same. Background art

A conventional surface acoustic wave device disclosed in Japanese Patent Application Laid-Open No. 3-143008 is a piezoelectric substrate and a migrating-resistant such as Cu, Ti, Ni, Mg, Pd provided on the piezoelectric substrate. It is equipped with an electrode of epitaxy-grown aluminum film that is oriented in a certain direction in the crystal orientation to which a small amount of additives with excellent properties are added. The film has a migration prevention function.

The electrode is a single-layer film composed of an epitaxially grown aluminum film, and the electrode grain size has grown to about the same as the film thickness. Therefore, if the electrode thickness exceeds a certain thickness, the electrode becomes brittle against the stress caused by the propagation of surface acoustic waves, and the power durability deteriorates. In particular, single-crystal film electrodes without grain boundaries form sub-grain boundaries when stress is applied for a long time, and as a result, stress concentrates at that portion, and conversely, it becomes brittle against stress accompanying the propagation of surface acoustic waves. Become. Disclosure of the invention

Provide a surface acoustic wave (S AW) filter with improved resistance to stress caused by propagation of a surface acoustic wave.

The SAW filter is provided on a substrate and the substrate, and the substrate And an electrode having a metal layer having a film thickness of 20 O nm or less and having an alignment film oriented in a certain direction with respect to the electrode.

The method for manufacturing the SAW filter includes a step of forming an electrode having a metal layer containing A1, and forming at least a part of the A1 diffusion prevention layer on the side wall of the electrode by sputtering etching simultaneously with the electrode. And a step of performing. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a surface acoustic wave (SAW) file according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of the SAW file in the embodiment. FIG. 3 is a cross-sectional view of a comb-shaped electrode which is a main part of the SAW filter according to Example 1 of Embodiment 1 of the present invention.

FIG. 4 is a cross-sectional view of a comb-shaped electrode, which is a main part of the SAW filter according to the second embodiment of the first embodiment.

FIG. 5 is a cross-sectional view of a comb-shaped electrode, which is a main part of the Saw fillet according to the third embodiment of the first embodiment.

FIG. 6 is a cross-sectional view of a comb-shaped electrode which is a main part of the SAW filter according to Example 4 of Embodiment 1.

FIG. 7 is a cross-sectional view of a comb-shaped electrode, which is a main part of the SAW fill in Comparative Example 1 of Embodiment 1.

FIG. 8 is a cross-sectional view of a comb-shaped electrode, which is a main part of the SAW filter in Comparative Example 2 of Embodiment 1.

FIG. 9 is a cross-sectional view of a comb-shaped electrode, which is a main part of the SAW filter according to Comparative Example 3 of the first embodiment.

FIG. 10 is a cross-sectional view of a comb-shaped electrode, which is a main part of the SAW filter according to Comparative Example 4 of the first embodiment. FIG. 11 is a cross-sectional view of a comb-shaped electrode which is a main part of a SAW filter according to Example 5 of Embodiment 2 of the present invention.

FIG. 12 is a cross-sectional view of a comb-shaped electrode which is a main part of the SAW filter according to the sixth embodiment of the second embodiment.

FIG. 13 is a cross-sectional view of a comb-shaped electrode, which is a main part of the SAW filter in Example 7 of Embodiment 2.

FIG. 14 is a cross-sectional view of a comb-shaped electrode, which is a main part of the SAW filter in Example 8 of Embodiment 2.

FIG. 15 is a cross-sectional view of a comb-shaped electrode which is a main part of the SAW filter in Comparative Example 5 of Embodiment 2.

FIG. 16 is a cross-sectional view of a comb-shaped electrode, which is a main part of a SAW filer, in Example 9 of Embodiment 3 of the present invention.

FIG. 17 is a cross-sectional view of a comb-shaped electrode which is a main part of the S AW filter in Example 10 of Embodiment 3.

FIG. 18 is a cross-sectional view of a comb-shaped electrode, which is a main part of the SAW filter according to Example 11 of the third embodiment.

FIG. 19 is a cross-sectional view of a comb-shaped electrode, which is a main part of the S AW filter in Example 12 of Embodiment 3.

FIG. 20 is a cross-sectional view of a comb-shaped electrode, which is a main part of a SAW filter in Comparative Example 6 of Embodiment 3.

FIG. 21 is a cross-sectional view of a comb-shaped electrode which is a main part of a SAW filter in Examples 13 and 14, and Comparative Examples 7, 8, 9, and 10 of Embodiment 4 of the present invention. ,

FIG. 22 is a cross-sectional view of a comb-shaped electrode that is a main part of the SAW file in Examples 15 and 16 of the fourth embodiment.

FIG. 23 is a cross-sectional view of a comb-shaped electrode, which is a main part of the SAW file in Examples 17 and 18 of the fourth embodiment. FIG. 24 is a cross-sectional view of a comb-shaped electrode which is a main part of a SAW filter in Examples 19 and 20 of Embodiment 5 of the present invention.

FIG. 25 is a cross-sectional view of a comb-shaped electrode which is a main part of the SAW file in Examples 21 and 22 of the fifth embodiment.

m 26 is a cross-sectional view of a comb-shaped electrode which is a main part of the SAW filter in Example 23 of Embodiment 5.

FIG. 27 is a cross-sectional view of a comb-shaped electrode, which is a main part of the SAW filter in Comparative Example 23 of the fifth embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1)

FIG. 1 is a perspective view of a surface acoustic wave (SAW) file according to an embodiment of the present invention, and FIG. 2 is a configuration diagram of a filter. The SAW filter is a so-called ladder-type surface acoustic wave filter having an elastic wave resonator consisting of a substrate 1 and an electrode 2 formed on the upper surface thereof, and having five resonators connected in a ladder type. The electrode 2 includes a comb-shaped electrode 21 and a reflector 22. In the embodiment of the present invention, substrate 1 is a 36 ° rotated Y-cut substrate of lithium tantalum san. In the first embodiment, a band-pass filter having a center frequency of 1.8 GHz and a pitch between combs of a comb-shaped electrode of about 0.6 m will be described.

FIGS. 3 to 6 are cross-sectional views of an electrode that is a main part of the SAW file of Examples 1 to 4 in the first embodiment. 7 to 10 are cross-sectional views of the electrodes of the SAW filters of Comparative Examples 1 to 4.

As shown in FIG. 3, the electrode 102 of Example 1 is the first layer 4 having a thickness of 20 nm formed on the substrate 1.

As shown in FIG. 4, the electrodes 112 of Example 2 are arranged in order from the substrate 1 side. A first layer 4 having a thickness of 20 O nm and a second layer 5 for preventing A1 atoms of the first layer from diffusing at the grain boundary in a direction perpendicular to the substrate.

As shown in FIG. 5, the electrodes 122 of Example 3 are sequentially laminated from the substrate 1 and have an underlayer 3 and a first layer 4 having a thickness of 20 nm.

As shown in FIG. 6, the electrodes 13 2 of Example 4 had an underlayer 3 laminated in order from the substrate 1, a first metal layer 4 having a thickness of 2 OO nm, and particles of the first metal layer. And a layer 5 for preventing field diffusion.

The electrode 144 of Comparative Example 1 is a metal layer 4 having a thickness of 20 nm formed on the substrate 1 as shown in FIG.

As shown in FIG. 8, the electrode 15 2 of Comparative Example 2 is a metal layer 4 having a thickness of 25 nm formed on the substrate 1.

As shown in FIG. 9, the electrode 16 2 of Comparative Example 3 was formed on the first metal layer 4 having a thickness of 2 OO nm and the A 1 atom substrate of the first metal layer, which were sequentially stacked from the substrate 1. A second metal layer 5 for preventing grain boundary diffusion in the vertical direction.

As shown in FIG. 10, the electrode 17 2 of Comparative Example 4 has a first metal layer 3 serving as an underlayer laminated sequentially from the substrate 1, and a second metal layer 200 μm thick. Layer 4.

Table 1 shows the material, film thickness, and film forming method of each layer of the electrodes of Examples 1 to 4 and Comparative Examples 1 to 4. (table 1 )

* IBS: Ion beam sputtering, DCMS: DC magnetron sputtering * In the column of material, * indicates an (111) oriented film.

* Unit of film thickness: nm As shown in Table 1, the metal mainly composed of A 1 or A 1 in the first embodiment is an A 1 ZrCu alloy. Except for Comparative Example 4, T i was used for the electrode having the underlayer and the second layer. In Comparative Example 4, Cr was used for the underlayer. Film formation was performed using either an ion beam sputter or a DC magnetron sputter. As a result of examining the electrode films by the X-ray diffraction method after the formation of these electrode films, the orientation of the electrodes was confirmed to be the same as in Examples 1, 2 and Comparative Example 2 in which the electrode films were formed by ion beam sputtering. In Example 3 and Example 4 in which Ti was used as the underlayer 3 and Example 4, only the peak of the (1 1 1) plane of A 1 was observed in the A 1 ZrCu layer, and the A 1 alloy layer was (1 1 1) It was confirmed that the film was an alignment film whose axis was oriented perpendicular to the substrate. Is the specific crystal plane for other electrode films? These peaks were not observed, confirming that the film was not an oriented film but a non-oriented polycrystalline film. The designed film thickness of the film used in the first embodiment is 20 O nm when the A 1 electrode is used. The deviation of the characteristics due to the electrode thickness and material was adjusted by changing the pitch of the comb-shaped electrode so that the center wave number was approximately 1.8 GHz. The electrodes were patterned by photolithography and dry etching. After pattern formation, the wafer was diced and divided into chips. The chips were die-bonded to a ceramic package and electrically connected by wire bonds. The lid was then welded and hermetically sealed in a nitrogen atmosphere to produce a SAW filter with electrodes.

For the filter created in this example, a signal of the highest frequency in the pass band, which is the weakest point of the ladder type filter, was applied to the device, and a power durability test was performed. The test was interrupted periodically after the start of the test, and the characteristics of the SAW filter were measured. The point at which the insertion loss of the passband increased by 0.5 dB or more was defined as device degradation, and the total test time until the device degraded after the start of testing was defined as the life. In the accelerated aging test, power and temperature were used as accelerated aging factors. A power accelerated aging test that measures the life under several applied powers while maintaining a constant chip surface temperature and a temperature accelerated aging test that measures the life under several applied chip temperatures while maintaining a constant applied power Two types of accelerated aging tests were performed during the test. Based on the results of these two tests, the life was estimated at an applied power of 1 W and an ambient temperature of 50 ° C using an Iring model. Regarding the power durability, a lifespan of 50,000 hours or more was used as a guide for evaluation. Table 2 shows the estimated lifetime of SAW filters with the electrodes shown in Table 1. Table 2 also shows the crystal grain size of each electrode film of the A 1 ZrCu gold layer. (Table 2)

From Table 2, the S AW filters using the electrodes of Examples 1 to 4 exceeded the estimated life of 50,000 hours, while the filters of Comparative Examples 1 to 4 were less than 50,000 hours. The crystal grain size of the AlZrCu layer was almost the same as the film thickness of each electrode. However, the filter of Comparative Example 2 has a lifespan not exceeding 50,000 hours, but has significantly improved power durability compared to other Comparative Examples. The difference between the electrode of Example 1 and the electrode of Comparative Example 2 is the film thickness and the crystal grain size. In the case of a conductor film, the crystal grain size increases in proportion to the film thickness. In a SAW device having a single-layer electrode of an alignment film as the electrode film, the lifetime exceeds 50,000 hours when the thickness of the electrode is less than 200 nm. However, in consideration of variations in power durability, the film thickness is preferably set to less than 100 nm. From these results, in order to obtain an electrode with high power durability, it is necessary that the layer mainly composed of A 1 or A 1 be made of an alignment film and have a small crystal grain size. To reduce the crystal grain size, it is effective to limit the film thickness.

(Embodiment 2)

FIGS. 11 to 14 are cross-sectional views of an electrode which is a main part of a surface acoustic wave (SAW) filter of Examples 5 to 8 in Embodiment 2 of the present invention. FIG. 15 is a sectional view of an electrode of the SAW filter of Comparative Example 5. As shown in FIG. 11, the electrode 18 2 of the fifth embodiment is the first layer 4 having a thickness of 20 nm formed on the top of the step 7 of the substrate 1. As shown in FIG. 12, the electrode 19 2 of Example 6 was formed on the top of the step 7 of the substrate 1, and the underlayer 3, which was sequentially laminated from the substrate 1, had a thickness of 200 nm. And a first layer 4.

As shown in FIG. 13, the electrode 202 of Example 7 is a first metal layer having a thickness of 200 nm, which is formed on the top of the step 7 of the substrate 1 and is sequentially stacked from the substrate 1. 4 and a second layer 5 for preventing grain boundary diffusion of the first metal layer.

As shown in FIG. 14, the electrode 211 of Example 8 has an underlayer 3 formed on the top of the step 7 of the substrate, which is laminated in order from the substrate 1, and a second layer having a thickness of 20 O nm. A first metal layer, and a second layer for preventing grain boundary diffusion of the first metal layer.

The electrode 222 of Comparative Example 5 is a metal layer 4 having a thickness of 30 nm formed on the substrate 1 as shown in FIG.

Table 3 shows the material, film thickness, and film forming method of each layer of the electrodes of Examples 5 to 9 and Comparative Example 5.

(Table 3)

* In the column of material, * indicates an orientation film of (111).

* Unit of film thickness: _nm

As shown in Table 3, A1MgCu alloy was used as the metal layer mainly composed of A1 or A1 in the second embodiment. Ti is used for the electrode having the underlayer and the second layer. Electrodes were formed by either ion beam sputtering or DC magnetron sputtering. With respect to these electrode films, the orientation of each electrode was examined by the 0-20 method of X-ray diffraction after forming the electrode films. Examples 5, 6, 7, 8 and Comparative Example 5 In each case, only the peak of the (1 1 1) plane of A 1 was observed in the Al Mg C Cu layer, and the A 1 alloy layer was oriented with the (1 1 1) axis oriented perpendicular to the substrate. It was confirmed that the film was formed. The configuration of the filter according to the second embodiment was the same as that of the first embodiment, and a filter having a center frequency of approximately 1.75 GHz using an A1 electrode having a designed thickness of 300 nm was tested. The center frequency was adjusted to approximately 1.75 GHz by changing the step of the step provided on the substrate for deviations in characteristics due to electrode thickness and material. Accordingly, the inter-electrode pitches of the comb-shaped electrodes of Examples 5 to 8 and Comparative Example 5 are almost the same. The electrodes were patterned by photolithography and reactive ion etching. As an etching gas, a mixed gas of BC13 and C12 was used. Accordingly, in reactive ion etching, pattern formation is performed by sputter etching with BC 13 + ions simultaneously with chemical etching with C 1 * radicals and BC 13 * radicals. The steps of the substrates in Examples 5 to 8 are formed by controlling the etching time. After pattern formation, the substrate is diced and divided, and each divided chip is die-bonded to a ceramic package. Further, each chip is electrically connected by a wire. Then, the lid was welded in a nitrogen atmosphere and hermetically sealed to produce a SAW filter having each electrode.

The power durability of the filter of the second embodiment was evaluated in the same manner as in the first embodiment. Table 4 shows the estimated lifespan of the SAW filter with the electrodes shown in Table 3. Table 4 also shows the crystal grain size of the A1MgCu layer 4 of each electrode film.

(Table 4)

As can be seen from Table 4, the estimated lifetime of the SAW filter using the electrodes of Examples 5 to 8 exceeded 50,000 hours as a guide, whereas the filter of Comparative Example 5 did not exceed 50,000 hours. In I got it. The crystal grain size of the A1MgCu layer was almost the same as the film thickness of each electrode. In the second embodiment, as described above, the designed film thickness of the A1 electrode in the filter is 30 O nm. By providing a step on the substrate and using this as a part of the electrode, and by setting the thickness of the metal layer mainly composed of A 1 or A 1 to 200 nm or less, the filter according to the first embodiment is used. It achieves the same level of power durability as the electrodes of Examples 1 to 4 shown, and achieves a life expectancy of 50,000 hours or more, which is a measure of power durability. Based on these results, we aim to achieve the desired characteristics and improve the power durability at the same time in a SAW filter that requires an electrode film thickness of 200 nm or more to achieve the desired filter characteristics. However, a step is provided on the substrate and this is used as a part of the electrode, and the layer mainly composed of A 1 or A 1 has a thickness of 200 nm or less to reduce the crystal grain size and to be an alignment film. It is effective. (Embodiment 3)

FIGS. 16 to 19 are cross-sectional views of an electrode which is a main part of a surface acoustic wave (SAW) filter of Examples 9 to 12 in Embodiment 3 of the present invention. FIG. 20 is a cross-sectional view of the electrode of the SAW filter of Comparative Example 6.

As shown in FIG. 16, the electrodes 2 32 of the ninth embodiment have a first metal layer 4 having a thickness of 20 nm and a first metal layer 4 having a thickness of 20 O nm, which are sequentially stacked from the substrate 1. It has a second layer 5 for preventing grain boundary diffusion in the direction perpendicular to the substrate of one atom, and a third layer 6 for adjusting the thickness of the electrode 232.

As shown in FIG. 17, the electrode 24 of Example 10 has an underlayer 3 laminated in order from the substrate 1, a first metal layer 4 having a thickness of 200 nm, and a first metal layer. Grain perpendicular to substrate of A 1 atom in layer 4 It has a second layer 5 for preventing field diffusion and a third layer 6 for adjusting the thickness of the electrode 242.

As shown in FIG. 18, the electrode 25 of Example 11 is formed on the top of the step 7 of the substrate 1 and has a first metal layer 4 having a thickness of 20 nm and a first metal layer 4. It has a second layer 5 for preventing the diffusion of A 1 atoms in the layer 4 in the direction perpendicular to the substrate, and a third layer 6 for adjusting the thickness of the electrode 25 2.

As shown in FIG. 19, the electrode 26 2 of Example 12 was formed on the top of the step 7 of the substrate 1, and the underlayer 3, which was stacked in order from the substrate 1, had a thickness of 200 nm. It has a first metal layer 4, a second layer 5 for preventing the grain boundary diffusion of the first metal layer 4, and a third layer 6 for adjusting the thickness of the electrode 26 2.

As shown in FIG. 20, the electrode 272 of the comparative example 6 includes an underlayer 3 laminated in order from the substrate 1 side, a first metal layer 4 having a thickness of 200 nm, and a first metal layer 4. It has a second layer 5 for preventing grain boundary diffusion of A 1 atoms in the layer 4 in a direction perpendicular to the substrate, and a third layer 6 for adjusting the thickness of the electrode 27 2.

Table 5 shows the material, film thickness, and film forming method of each layer of the electrodes of Examples 5 to 9 and Comparative Example 5.

(Table 5)

«IBS: Ion beam sputtering, DCMS: DC magnetron sputtering * In the column of material, * indicates an (111) oriented film.

* Unit of film thickness: _{nm As shown in} Table 5, Al Mg alloy was used as the metal mainly composed of A 1 or A 1 in the third embodiment. T i is used for the underlayer and the second layer. The layer was formed by either ion beam sputtering or DC magnetron sputtering. Regarding the orientation of each electrode examined by the 0-26 method of X-ray diffraction after forming the electrode film, any of Example 9, Example 10, Example 11, Example 12, and Comparative Example 6 was used. In the Al Mg layer as well, only the peak of the (1 1 1) plane of A 1 is observed, and the A 1 alloy layer is an oriented film in which the (1 1 1) axis is oriented perpendicular to the substrate. Was confirmed. However, since the electrode had two A1Mg layers, a first layer and a third layer, samples of the underlayer and the first layer were separately prepared under the same film forming conditions, and the orientation was confirmed. The configuration of the filter used in the third embodiment is the same as that of the first embodiment.However, a filter having a design thickness of 480 nm and an A1 electrode has a center frequency of approximately 800 MHz. It is. For the deviation of the characteristics due to the electrode thickness and material, refer to the step on the substrate. By changing the thickness of the third layer and the third layer, the filter was adjusted so that the center frequency was approximately 800 MHz. Therefore, the inter-electrode pitches of the comb-shaped electrodes of Examples 9 to 12 and Comparative Example 6 are almost the same. The electrodes and the filter were made in the same manner as in the second embodiment.

Also in the third embodiment, the power durability of the filter was evaluated in the same manner as in the first embodiment. Table 6 shows the estimated lifetime of each Saw filter having each electrode shown in Table 5. Table 6 also shows the crystal grain size of the A1Mg layer, which is the first layer of each electrode film.

(Table 6)

* The crystal grain size indicates the crystal grain size of the first layer.As can be seen from Table 6, the estimated lifetime of SAW finole using the electrodes of Examples 9 to 12 exceeds 50,000 hours. On the other hand, in Comparative Example 6, the time was 50,000 hours or less. The crystal grain size of the A 1 Mg layer, which is the first layer of each electrode film, was almost the same as the thickness of each electrode. In the second embodiment, the designed film thickness of the A1 electrode of the filter used as described above is 480 nm, but the above-mentioned A1 or A1 is mainly formed on the first layer mainly composed of A1. By providing a second layer for limiting the layer thickness of the first layer and a third layer for adjusting the electrode thickness, or by providing a step on the substrate and making this a part of the electrode, The thickness of the metal layer is 200 nm or less. As a result, the city has high power durability and a lifespan of 50,000 hours or more, which is a measure of power durability. Example 9 and Example 10 After the test, it was observed that hillocks were formed on the surface of the comb-shaped electrode by diffusion of A 1 in areas other than the area where the electrode was deteriorated. The diffusion of these A 1 atoms is due to the third deterioration, which is the thickness adjustment layer. On the other hand, since it was not observed in Examples 11 and 12, the thickness of A 1 or the third layer mainly composed of A 1 is also set to a thickness of 200 nm or less. It is preferable. Further, a fourth layer for suppressing the diffusion of A 1 atoms from the third layer may be provided on the third layer. For the electrodes of Examples 11 and 12, and Comparative Example 6, when the electrodes after the test were observed, hillocks due to diffusion of A1 atoms were not observed on the electrode surface, but the comb-shaped electrodes were observed. It was observed that they occurred in the form of side hillocks in between. From these results, it is possible to realize the characteristics of a SAW filter that requires an electrode film thickness of 200 nm or more for the desired filter characteristics, and at the same time to improve the power durability, 1 or a second layer for limiting the thickness of the first layer and a second layer for adjusting the electrode thickness on the first layer having a thickness of 200 nm or less and mainly containing A 1. The third layer is provided. In order to prevent the third layer from becoming thicker, provide a step on the substrate and use this as a part of the electrode.The thickness of the layer mainly composed of A 1 or A 1 should be 20 nm or less. Can reduce the crystal grain size.

(Embodiment 4)

FIGS. 21 to 23 are cross-sectional views of an electrode which is a main part of a surface acoustic wave (SAW) filter of Examples 13 to 18 in Embodiment 4 of the present invention. The sectional views of the electrodes of the SAW filters of Comparative Examples 7 to 10 are the same as the electrodes of FIG.

As shown in FIG. 21, the electrodes 28 of Examples 13 and 14 A first metal layer 4 mainly composed of A 1 or A 1 and having a thickness of 200 nm, which is stacked in order from 1 and a direction perpendicular to the substrate of the A 1 atom of the first metal layer. And a third layer 6 for adjusting the film thickness of the electrode 28 2. On the side wall of the electrode 282, a diffusion preventing layer 8 for preventing the grain boundary diffusion of A1 atoms of the first metal layer 4 is formed. The diffusion preventing layer 8 does not reach the substrate as shown in FIG.

As shown in FIG. 22, the electrodes 292 of Examples 15 and 16 each have an underlayer 3 laminated in order from the substrate 1, a first metal layer 4 having a thickness of 200 nm, The first metal layer 4 includes a second layer 5 for preventing A1 atoms from diffusing in the direction perpendicular to the substrate, and a third layer 6 for adjusting the thickness of the electrode 292. On the side wall of the electrode 292, a diffusion prevention layer 8 for preventing the grain boundary diffusion of A1 atoms of the first metal layer 4 is formed. Although the diffusion prevention layer 8 does not reach the substrate as shown in FIG. 22, a part of the side walls of the first metal layer 4, the second layer 5, the third layer 6 and the underlayer 3 is provided. Is covered.

The electrodes 30 2 of Examples 17 and 18 are formed on the top of the step 7 of the substrate 1 as shown in FIG. 23, and the first metal layer 4 having a thickness of 200 nm The second layer 5 for preventing the grain boundary diffusion of the A 1 atom of the first metal layer 4 in the direction perpendicular to the substrate, and the third layer 6 for adjusting the thickness of the electrode 302 are Have. On the side wall of the electrode 302, a diffusion preventing layer 8 for preventing the A 1 atom of the first metal layer 4 from diffusing at the grain boundary is formed. The diffusion preventing layer 8 does not reach the bottom of the substrate as shown in FIG. However, the diffusion preventing layer 8 covers the side walls of the first metal layer 4, the second layer 5, the third layer 6, and a part of the side wall of the step 7 of the substrate 1.

The electrodes of Comparative Examples 7, 8, 9, and 10 were the same as in Examples 13 and 14. The configuration shown in Fig. 21 was adopted.

Table 7 shows the material, film thickness, and film forming method of each layer of the electrodes of Examples 13 to 18 and Comparative Example 7 10.

(Table 7)

* IBS: Ion beam sputtering, DCMS: DC magnetron sputtering

* In the column of material, * indicates an orientation film of (111).

* Unit of film thickness: nm As shown in Table 7, A 1 Mg alloy was used as the metal 4 mainly composed of A 1 or A 1 in the fourth embodiment. Ti was used for the underlayer. In Examples 13 and 15, Examples 15 and 17, Comparative Examples 7 and 8, the second layer has Ti, and Examples 14 to 16 and Examples 18 and 18 and Comparative Examples 8. In Comparative Example 10, Cu was used for the second layer. The layer was formed by either ion beam sputtering or DC magnetron sputtering. this Regarding the orientation of each electrode examined by the 0-20 method of X-ray diffraction after forming these electrode films, all of Examples 13 to 18 and Comparative Examples 9 and 10 were Al In the Mg layer, only the peak of the (1 1 1) plane of A1 was observed, and the A 1 alloy layer was an oriented film with the (1 1 1) axis oriented perpendicular to the substrate. confirmed. However, since there are two A1Mg layers, the first and third layers, a sample of two layers, an underlayer and a first layer, was separately prepared under the same film forming conditions, and the orientation was confirmed. In Comparative Examples 7 and 8, no peak was observed from a specific crystal plane, confirming that the film was not an oriented film but a non-oriented polycrystalline film. The configuration and design of the filter used in the fourth embodiment are the same as in the third embodiment of the invention. All electrodes were patterned by ion milling with Ar + ions. Since the ion milling method physically forms a pattern by sputtering, a part of the sputtered atoms adheres to the side wall of the electrode, and a diffusion preventing layer is formed simultaneously with the pattern formation. However, the electrode side wall cannot be completely covered, and the diffusion preventing layer is not formed to the bottom of the substrate.

Table 8 shows the estimated lifetime of each SAW filter with each electrode shown in Table 7. Table 8 also shows the crystal grain size of the AlMg layer as the first layer of each electrode film.

(Table 8)

* The crystal grain size indicates the crystal grain size of the first layer. <Table 8> As can be seen from Table 8, the estimated lifetime of the SAW filter using the electrodes of Examples 13 to 18 was 50,000 hours as a guide. Compared to the comparison example? The filter of ~ 10 was less than 50,000 hours. The crystal grain size of the Al Mg layer of the first layer of each electrode film was almost the same as the layer thickness of each electrode. In Examples 13 and 14, and Comparative Example, after the test, it was observed that side hillocks were formed on the side walls of the comb-shaped electrodes other than the portions where the electrodes were deteriorated. The side hillocks were generated between the substrate and the diffusion preventing layer for preventing the A1 atom in the first metal layer provided on the side wall of the electrode from diffusing at the grain boundary. In Examples 15 to 18, no electrode deterioration was observed except for the portions where the electrodes were deteriorated. Therefore, since the diffusion barrier layer partially covers the underlayer or part of the side wall of the substrate step and completely covers the first metal layer, the grain boundary of A 1 atoms on the electrode side wall is formed. It is considered that diffusion was suppressed. Also, the filter using Cu for the second metal layer has improved power durability compared to the filter using Ti. Cu is the self-diffusion coefficient of A 1 Since Cu is a metal with a larger diffusion coefficient for A 1 than in the above, Cu diffuses into the grain boundaries of the second layer in the heating step during the device fabrication process, and the grain boundary diffusion path of A 1 atoms is changed by Cu atoms. Will be blocked. Therefore, it is considered that the grain boundary diffusion of A 1 atoms in the horizontal direction in the substrate was also suppressed. Cu not only easily diffuses into A 1, but also easily forms an intermetallic compound with A 1, and the second layer has a large grain size. As a result, the effect of suppressing A1 atoms greatly changes depending on the temperature change during the process and the thickness of the Cu layer, etc., and the resistance value of the electrode film is also likely to increase. There were many. Therefore, the second layer using a metal with a larger diffusion coefficient for A1 than the self-diffusion coefficient for A1 has a large effect on power durability, but each filter has an optimum value for the layer thickness, and process control In particular, it is necessary to control the heating process. In particular, when the thickness of the first layer of the metal mainly composed of A 1 or A 1 is less than 200 nm, the thickness of the second layer of Cu is less than 20 nm, preferably It is desirable that the thickness be 10 nm or less. Further, the heating step in the process is desirably 250 ° C or less, preferably 200 ° C or less. The second layer using a metal having a smaller diffusion coefficient for A1 than the self-diffusion coefficient for A1 was mainly composed of A1 or A1. Although the effect of suppressing grain boundary diffusion in the horizontal direction is not so expected, the power durability and characteristics of the filter were stable. From these results, the diffusion suppressing layer that suppresses the grain boundary diffusion of A 1 atoms from the first layer of A 1 or the metal mainly composed of A 1 to the substrate in the horizontal direction is the same as that of the first layer. It is effective to completely cover the side wall. The method of forming the diffusion suppression layer is to form the pattern by sputtering etching and to provide an underlayer or to cut the substrate to form a step. Is valid. In addition, the diffusion suppressing layer formed on the electrode side wall by this method naturally becomes an alloy layer or a laminated film of A 1 or a first metal layer mainly composed of A 1 and a base layer or a substrate material. Good oneness.

(Embodiment 5),

FIGS. 24 to 26 are cross-sectional views of an electrode which is a main part of the surface acoustic wave (SAW) filter of Examples 19 to 23 in the fifth embodiment. FIG. 27 is a cross-sectional view of an electrode of the SAW filter of Comparative Example 11. The electrodes 3 12 of Examples 19 and 20 are formed on the top of the step 7 of the substrate 1 as shown in FIG. 24, and the first metal layer 4 having a thickness of 200 nm A second layer 5 for preventing grain boundary diffusion of A 1 atoms of the first metal layer in a direction perpendicular to the substrate; and a third layer 6 for adjusting the thickness of the electrode 312. Further, after the electrode pattern is formed, a protective film 9 made of silicon nitride having a thickness of 100 nm in Example 19 and silicon oxide having a thickness of 100 nm in Example 20 is formed on the electrode 312. . As a result of observation with an electron microscope, as shown in Fig. 24, the protective film was not sufficiently formed at the boundary between the comb-shaped electrode on the substrate step and the bottom of the substrate between the electrodes, and was discontinuous. Had become.

As shown in FIG. 25, the electrodes 32 2 of Examples 21 and 22 each have an underlayer 3 laminated in order from the substrate 1, a first metal layer 4 having a thickness of 200 nm, The first metal layer includes a second layer 5 for preventing grain boundary diffusion of A 1 atoms in a direction perpendicular to the substrate, and a third layer 6 for adjusting the thickness of the electrode 3 22. After the formation of the electrode 32 2, a protective film 9 made of silicon nitride having a thickness of 10 O nm in Example 21 and a silicon oxide having a thickness of 10 O nm in Example 22 is formed on the electrode 3 22. . In observation with an electron microscope, the protective film 9 was The film was not sufficiently formed at the boundary between the underlayer 3 and the bottom of the substrate 1 and was discontinuous.

As shown in FIG. 26, the electrode 33 of Example 23 has an underlayer 3 laminated in order from the substrate 1, a first metal layer 4 having a thickness of 200 nm, and a first metal layer 4. It has a second layer 5 for preventing grain boundary diffusion in the direction perpendicular to the substrate of A 1 atoms of the layer, and a third layer 6 for adjusting the thickness of the electrode 33 2. After the formation of the electrode 3332, a 50-nm-thick silicon nitride 9a and a 50-nm-thick silicon oxide 9b are formed on the electrode 3332. According to observation with an electron microscope, as shown in Fig. 26, the protective films 9a and 9b are not sufficiently formed at the boundary between the underlayer 3 and the bottom of the substrate 1 and become discontinuous. I was

As shown in FIG. 27, the electrode 3 42 of Comparative Example 11 has a first metal layer 4 having a thickness of 20 O nm and the first metal layer A 1 in a direction perpendicular to the substrate. It has a second layer 5 for preventing grain boundary diffusion, and a third layer 6 for adjusting the thickness of the electrode 34 2. After the formation of the electrode, a protective film 9 made of silicon nitride having a thickness of 100 nm is formed on the electrode 342. Observation with an electron microscope showed that the protective film 9 was not sufficiently formed at the boundary between the electrode 342 and the bottom of the substrate 1 and was discontinuous, as shown in FIG.

Table 9 shows the materials, film thicknesses, and film forming methods of each layer of the electrodes of Examples 19 to 23 and Comparative Example 11. (Table 9)

As shown in Table 9, A 1 Mg alloy was used as the metal mainly composed of A 1 or A 1 in the fifth embodiment. For the underlayer 3 and the second layer 5, T i was used. These layers were formed by either ion beam sputtering or DC magnetron sputtering. According to the 0-20 method of X-ray diffraction after the formation of these electrode films, the orientation of each electrode was as follows. Only the peak of the (111) plane was observed, confirming that the A1 alloy layer was an oriented film in which the (111) axis was oriented perpendicular to the substrate. However, since all samples have two A1Mg layers, the first and third layers, samples of the first layer or the underlayer and the first layer were separately prepared under the same deposition conditions. The orientation was confirmed. The configuration of the filter used in the fifth embodiment is the same as that of the first embodiment. When the designed film thickness of 480 nm A1 electrode is A filter with a wave number of approximately 800 MHz was used. The electrodes were formed by photolithography and dry etching. After the formation of the electrode, a protective film is formed, and then the protective film in a portion where the electrode is electrically connected is removed by etching. Then, the resonator was face-down mounted on the alumina board. In the fifth embodiment, the filter is not hermetically sealed. Also in the fifth embodiment, the power durability of the filter was evaluated in the same manner as in the first embodiment. The filter was evaluated under the condition that the surface was exposed to the air, although the protective film was formed. Table 10 shows the estimated lifetime of each SAW filter having each electrode shown in Table 9. Table 10 also shows the crystal grain size of the A1Mg layer as the first layer of each electrode film.

(Table 10)

* The crystal grain size indicates the crystal grain size of the first layer. As can be seen from Table 10, the SAW filters using the electrodes of Examples 13 to 18 exceeded the estimated life expectancy of 50,000 hours, while the filters of Comparative Examples 7 to 10 used the filters. Was less than 50,000 hours. The crystal grain size of the Al Mg layer of the first layer of each electrode film was almost the same as the layer thickness of each electrode. When Examples 19 and 20 were compared with each other and Examples 21 and 22 were compared, the filter having the protective film of silicon nitride was the same as the filter having the protective film of silicon oxide. It can be seen that the power durability is improved as compared with. With the silicon nitride protective film, a slight deterioration in the electrical characteristics of the film after formation was observed as compared to before the formation. There was no change in the electrical characteristics of the silicon oxide protective film before and after its formation. In the filter of Example 23 having a protective film laminated with silicon nitride and silicon oxide, the electrical characteristics did not change before and after the protective film was formed, and the power durability was the same as when silicon nitride was used alone. Significant improvement was seen. Although the filter of Comparative Example 11 has almost the same electrode configuration as that of Example 13 of Example 4, and has a structure with excellent power durability, the estimated life is as short as 320 hours. This is considered to be because the hermetic sealing was not performed in the fifth embodiment. The filters of Examples 19 to 23 have almost the same power durability as those of the filters hermetically sealed. From this, the filter of Comparative Example 11 was caused by the fact that the first layer of the metal mainly composed of A1 or A1 was not completely covered with the protective film but was partially exposed. It is considered that the life is short. Discontinuous portions of the protective film as shown in FIGS. 25 to 27 are likely to be formed at the boundary between the electrode and the bottom of the substrate between the electrodes having a thin protective film. If a discontinuous portion is formed, providing a step on the substrate as in Embodiment 5 or using a metal underlayer with excellent moisture resistance is effective in extending the life of the filter. You can see that. '

The protective film suppresses the generation of hillocks caused by the A 1 atom middleing of the electrode, improves power durability, prevents short-circuiting between the electrodes, and improves moisture resistance.

In the fifth embodiment, the electrode structure for the purpose of achieving both the power resistance and the moisture resistance by the protective film has been described. Providing a step on the substrate or an electrode with an underlayer with excellent moisture resistance as the underlayer On the other hand, forming a protective film is effective in extending the life of the film.

In the first to fifth embodiments, the structure of the electrode is described using a specific filter. Each film configuration, film thickness, material, etc. are not limited to these. In particular, it is desirable that the thickness of the layer mainly composed of A 1 or A 1 be equal to or less than 0.00IL with respect to the width L of the electrode of the SAW filter. As a result, the conductor powder is sufficiently miniaturized, and the stress applied to the electrode due to the propagation of the surface acoustic wave can be sufficiently dispersed. Industrial applicability

The present invention provides a surface acoustic wave filter having improved resistance to stress caused by the propagation of surface acoustic waves, and a method for manufacturing the same.

Claims

The scope of the claims

1. The substrate and

An electrode provided on the substrate and having a first layer having a thickness of 200 nm or less, which is an alignment film oriented in a certain direction with respect to the substrate;

Surface acoustic wave (S AW) filter with

2. The S AW filter according to claim 1, wherein the first layer is made of a metal containing A1.

3. The metal containing A1 is A1 alone or an alloy in which A1 contains at least one of Mg, Zr, Cu, Sc, Ti, and Ta. S AW filter according to paragraph 2.

4. The SAW according to claim 2, wherein the electrode further has a second layer provided on the first layer, for preventing grain boundary diffusion of the first layer. filter.

5. The SAW filter according to claim 4, wherein the electrode further has a third layer provided on the second layer for adjusting the thickness of the electrode.

6. The SAW filter according to any one of claims 2 to 5, further comprising a grain boundary diffusion preventing layer provided on the electrode.

7. The grain boundary diffusion preventing layer is made of a material containing a metal having a smaller diffusion coefficient for A 1 than the self diffusion coefficient of A 1. SAW filter according to clause 6.

8. The S AW filter according to claim 7, wherein the metal having a smaller diffusion coefficient for A1 than the self-diffusion coefficient of A1 is one of Ti, Ta, W, and Cr. .

9. The S AW filter according to claim 6, wherein the grain boundary diffusion preventing layer is made of a material containing a metal having a larger diffusion coefficient for A 1 than the self diffusion coefficient of A 1.

10. The S according to claim 9, wherein the metal having a larger diffusion coefficient for A 1 than the self-diffusion coefficient of A 1 is one of Cr, Pd, and Mg. AW Phil evening.

11. The SAW filter according to any one of claims 2 to 10, further comprising an A1 atomic diffusion preventing layer provided on a side wall of the electrode.

12. The SAW filter according to claim 11, wherein the A 1 atomic diffusion preventing layer covers a side wall of the first layer.

1 3. The SAW filter according to any one of claims 1 to 12, further comprising a protective film that covers at least a part of the electrode. 14. The SAW filter according to claim 13, wherein said protective film is made of silicon nitride.

15. The SAW filter according to claim 13, wherein said protective film comprises a laminated film of silicon nitride and silicon oxide.

1 6. The substrate has a step,

The electrode is provided on a top of the step,

S AW filter according to any one of Items 1 to 10.

17. The SAW filter according to claim 16, further comprising an A1 atom diffusion preventing layer provided on a side wall of said electrode.

18. The SAW filter according to claim 17, wherein the A1 atomic diffusion preventing layer covers a side wall of the first layer.

19. The S AW filter according to claim 18, wherein said A 1 atomic diffusion preventing layer covers at least a part of a side wall of said stepped portion.

20. The SAW filter according to any one of claims 16 to 19, further comprising a protective film that covers at least a part of the electrode. 21. The SAW filter according to claim 20, wherein said protective film covers at least a part of a side wall of said step portion. ,.

22. The S AW filter according to claim 20 or 21, wherein said protective film is made of silicon nitride.

23. The SAW filter according to claim 20, wherein said protective film comprises a laminated film of silicon nitride and silicon oxide.

24. The SAW filter according to any one of claims 1 to 10, wherein the electrode further has an underlayer provided between the substrate and the first layer. 25. The S AW filter according to claim 24, further comprising an A 1 atomic diffusion preventing layer provided on a side wall of said electrode.

26. The SAW filter according to claim 25, wherein said A 1 atomic diffusion preventing layer covers a side wall of said first layer.

27. The SAW filter according to claim 26, wherein said A1 atomic diffusion preventing layer covers at least a part of a side wall of said underlayer.

28. The Saw filter according to any one of claims 24 to 27, further comprising a protective film that covers at least a part of the electrode.

29. The SAW filter according to claim 28, wherein said protective film covers at least a part of a side wall of said base layer. 30. The SAW filter according to claim 28, wherein said protective film is made of silicon nitride.

31. The SAW filter according to claim 28, wherein said protective film comprises a laminated film of silicon nitride and silicon oxide.

3 2. forming an electrode having a metal layer containing A 1 on the substrate; Forming at least a part of the A 1 diffusion prevention layer at the same time as the electrode on the side wall of the electrode by sputtering etching.